Fuck. That's a good question. Militaries definitely use dogs. If they are considered equipment, I don't see why that wouldn't make them an arm. Sure you could argue fatigues are equipment but not arms, but I would counter with 'they don't use their pants to attack enemies'.
On the other hand, I guess a Jeep isn't a bearable arm and it's almost as dangerous as a pit bull. We clearly need some trailer park trash to win the lottery so we can get a legal precedent on this.